Winter in the West has been alarmingly mild. Here’s why that’s bad.

While the East may have been plunged into a snowy deep freeze this winter, weather data shows something perhaps more notable is happening in the West, where snowpack has been low and temperatures high.

In fact, much of the West is on track for one of its mildest winters on record, according to a recent report from Weather.com.

For example, people in normally snowy Salt Lake City have barely seen a flake of snow and Phoenix is sweltering through its warmest winter since records began, according to AccuWeather meteorologist Paul Pastelok.

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And overall, despite the eastern chill, amazingly it’s the fifth-warmest start to winter since 1981 when the entire country is figured in, Washington Post meteorologist Ben Noll said on X.

Low snowpack in West prompts worries

Mountainous snow is vital for ski tourism and as a source of water, so the lack of snow in the West is worrisome, experts said.

“Snowpack is of critical economic and ecological importance to Western communities,” according to a recent report from the National Oceanic and Atmospheric Administration. “Consequential economic impacts have already occurred, especially for the recreation sector and the communities that rely on it. Water supply concerns continue to increase, impacting key economic sectors like agriculture, recreation, and energy.”

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The Weather.com report said that the West relies heavily on the mountain snowpack that builds up over the winter as a source of water throughout the year, which is steadily released into rivers and reservoirs as temperatures climb in spring and summer.

Much of the recent precipitation has fallen as rain, not snow. “Precipitation falling as rain tends to run off before it can recharge reservoirs and groundwater,” according to a release from NASA. “On the other hand, winter snowpack that melts in the spring can produce a more metered, sustained water supply. “

“The health of the mountain snowpack has implications for ecosystems, wildfire dynamics, and water availability for agriculture and other uses during drier times of the year,” the NASA release said.

How dire is the situation in the West?

Snow cover across the Western United States on Feb. 1 was 139,322 square miles − the lowest Feb. 1 snow cover in the satellite record (since 2001), according to NOAA.

Also, as of Feb. 1, Oregon, Colorado, and Utah have reported record low statewide snowpack. Widespread snowpack records go back to the early 1980s, NOAA said.

Specifically, “a January dry spell resulted in most states receiving 50% or less of normal precipitation,” the NOAA report said. “Combined with above-normal temperatures and sunny days, this resulted in little snow accumulation and some snowmelt across the West. Historically, January is a significant snow accumulation month for much of the Pacific Northwest and northern Rockies.”

Why has it been so cold and snowy in the East but so warm and dry in the West?

A ridge of high pressure has dominated the western half of the country, allowing for consistent warmer weather to prevail as well as causing the jet stream to steer storms farther north, limiting snowfall for the mountains, the Weather.com report said.

Randall Cerveny, a geographer at Arizona State University, explained further in an email to USA TODAY: “Very often the atmosphere over North America acts in a pronounced ‘see-saw’ pattern as a result of something called the ‘Pacific-North American’ teleconnection.”

“In its positive phase (which is what we are currently in), we have a jet stream arching northward over the western half of the country (in which we call an upper level ‘ridge’) and dipping far south over the eastern half of the country (in which we call an upper level ‘trough’).”

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Cerveny said, “This means that warm air from the tropics and subtropics moves northward over the western half of the country (making the Southwest hot) and cold air pours south from the arctic into the eastern half of the country (making the East cold).”

Pastelok said this overall pattern from the northern Pacific to the northern Atlantic has not changed dramatically over the winter season.

In addition, he said the cold in the East was also boosted by a few unwelcome appearances from the polar vortex.

Pattern shift ahead?

According to the NOAA report, a pattern shift is expected across the West with wetter-than-normal conditions favored over the next two weeks. However, warmer-than-normal temperatures are still favored for large parts of the West, which could further inhibit snowpack development.

“Time is running short on reaching average peak median snow water equivalent, which occurs in March and April in most basins in the West. Snowfall deficits will be difficult to make up, but abundant snowfall over the next couple months could reduce impacts,” the report concluded.

This article originally appeared on USA TODAY: Winter weather in the west has been alarmingly mild. What to know